Encouraging Beneficial Insects Pays Off

Not sure you want insects in your garden? We hope we can convince you they are an excellent sign of a healthy ecosystem, as insects play a vital ecological role, especially for gardeners. Read on to learn more about the relationship between thriving gardens and the wonderful insects they support.

A large portion of the insect pests that cause severe damage are non-native insects, like the Japanese Beetle (Popillia japonica), pictured above, imported from Japan on a shipment of plants in the early 1900s. Pests like these can be a big issue for farmers and home gardeners alike.

If minimizing destructive insects in your gardens is the goal, embracing and supporting native insects and plants is an excellent strategy.

Many species of insects, called beneficial insects, actually hunt and kill several of those insect pests you would like to see less of in your garden. One example is the blue-winged wasp (Scolia dubia) which lays its eggs in the grubs of Japanese beetles. These parasitoids help reduce the numbers of Japanese Beetles that reach maturity and then find their way onto your rose bushes and green beans.

To attract beneficial insects, establish native plants, like this Golden Alexander (Zizia aurea). This carrot family flower blooms early in the season in the east and midwest, which helps attract numerous insects. Ladybugs, another effective beneficial insect, can be found hunting for smaller insects on Golden Alexander. It is also a host plant for Swallow-tail Butterfly caterpillars, a beautiful, native pollinator.

Studies conducted by Karin T. Burghardt and Douglas W. Tallamy from the University of Delaware, demonstrated that native plants support a larger, more diverse insect population. In field studies comparing native to non-native landscapes, insects deposited more eggs in the plots planted with native vegetation.

…up to 90% of all species of insect herbivores can successfully reproduce only on plant lineages with which they have shared an evolutionary history.

Weiss & Berenbaum

Insects use visual and chemical signals when interacting with plants. This communication system between plant and insect, which has evolved over time, has created relationships that ensure foraging and reproductive success. This is why planting native plants are essential for attracting and supporting native, beneficial insects.

A good example of one of these plants is the genus Asclepias, commonly referred to as milkweed. The Monarch Butterfly, the Milkweed Leaf Beetle, and a handful of other insects have a long evolutionary relationship with milkweed making it an essential habitat requirement for their reproduction.

Milkweed flowers in the middle of the season, attracting and supporting a variety of other insects looking to feed on nectar or smaller insects in the garden. The ants in the image above are foraging on a milkweed pod.

Having late-season, flowering plants will also continue to benefit the insects in your gardens. Consider encouraging species in the genus Solidago, commonly known as goldenrods. There are between 100-200 different species, subspecies, and varieties of goldenrod that grow in a multitude of habitats. Most goldenrod are native to the United States and there is least one species that is native to every region.

In addition to providing late-season nectar for bees, butterflies and other pollinators, late-season, native flowers also attract excellent beneficial insects, like the lacewings and praying mantis.

Garden space is valuable. As gardeners we are constantly debating whether we have enough room to plant everything we want. If you want a garden that is ecologically balanced, it is important to devote a good portion of that space to flowering native plants. They serve the valuable role of attracting beneficial insects, which contribute to your garden’s success. You may even see decreased plant damage and increased biodiversity. Encouraging beneficial insects could even make it easier to skip the chemical pesticide applications.